Aluminum wire (electricians or really experienced people only please).?
Aluminum wire isn't used much anymore, partly due to it's tendancy to work harden and get brittle. Most electricians I work with prefer not to use it. I would opt for your thought of installing a junction box and changing to copper wire for the rest of the run. Code would allow this, and it would be good insurance against future trouble with the aluminum wire at the termination of that circuit. Don't forget the anti -ox.
OK. the first thing is that you can connect copper to aluminum. They make wire that is called copper clad aluminum and is exactly what it sounds like, but you don't have to install that. So if you want to install a junction box just make sure that it remains exposed and that you secure the wire within 12 inches of the box. About your light. I would simply put up another fixture, just make a visual inspection of the wire. if it is all roughly the same shade then it is most likely still fine. The only damage that is done by replacing a fixture to much is to the wire that is inside of the box and if something happens to that it will not start a fire, the light simply won't work.
You can never ever connect an Aluminum wire to a Copper wire. Never, copper in contact with aluminum and a bit of moisture acts like a Battery. Remember the old Grade School experiment where students made a battery using copper pennies and aluminum foil by simply contacting the foil to several pennies, then lighting a neon bulb! So copper in contact with aluminum creates a galvanic action due to potential difference and thus can cause a hot spot and a fire can literally break out in the junction box where you made the connection. Keep this always in mind since you have a whole house of that aluminum wire. To connect aluminum wire to a fixture you need a fixture that will accept an aluminum wire. Check that with the hardware or where or Lowes or wherever you buy the fixture from. There are fixtues with contacts points for wire in them that accept both copper and aluminum wire. So you do not need to replace the wire just to install the fixture. Or you can go to Lowes and get a special connector that safely connects the aluminum wire to a short piece of copper wire and then connect that copper pigtail piece to any fixture you buy. The danger of aluminum wire has never been that becomes brittle, but that corrosion forms at screw joints in the switches, outlet boxes and the like, that causing a resistance and that resistance acting literally like a heater and becoming red hot and starting a fire.
yes aluminum wire is susceptible to stress and braking but only if there is a stress bend or over twisting the wire. As long as you aren't stressing the wire ie: bending repeatedly where it's tacked down or over twisting the ends (which will break on copper as well) then you shouldn't have any problems. just be sure to support any heavy fixtures as the weight can stress the wire. I hope this helps
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